Nuclear Magnetic Resonance and Magnetization Studies of CdCr2Se4

Abstract

We have investigated the NMR lineshapes and temperature dependences of 53Cr and 77Se in the ferromagnetic spinel CdCr 2 Se 4 . The internal magnetization directions are determined by shape anisotropy, so that the observed lineshapes are powder patterns extensively broadened by anisotropic dipolar and (for 53Cr) quadrupolar interactions. The 0°K values for the central frequencies are 44.0 and 80 MHz for 53Cr and 77Se, respectively. The temperature dependence of the bulk magnetization was carefully measured and is in close agreement with that of the 53Cr (or 77Se) resonance frequency. The 53Cr resonance signal could not be followed above 120°K because of increasingly rapid relaxation. Up to 100°K the dependence is described by M = M 0 (1−3.11×10 −4 T 3/2 ) . Although the absence of other terms in T is not understood, the T 3/2 coefficient is derivable from a simple spin‐wave calculation on the basis of the approximate model with two exchange interactions given by Baltzer, Wojtowicz, Robbins, and Lopatin.